This invention relates to fluid measuring devices, and more particularly to devices for measuring the concentration of water in a fluid mixture of ink and water, particularly mixtures of lithographic ink and water.
Better results are obtained from a printing press if the relative amounts of water or aqueous dampening solution and ink in the ink mixture are maintained at optimum levels. This can be accomplished at the beginning of a printing press operation by initially mixing the water or aqueous solution and ink in the proper proportions. However, over a period of time the proportions of ink and water in the recirculating ink mixture can change as printing progresses. Until recently, the printer attending the press had no means of automatically and continuously monitoring the concentration of water in a recirculating ink-water mixture. Rather, he had to rely upon his experience and examination of the printing results to estimate the dampening liquid concentration.
An automatic meter for measuring the concentration of water in an ink-water mixture is disclosed in U.S. patent application Ser. No. 616,106, filed June 1, 1984 by Goldberg et al. In this system an ink-water mixture flows through a capacitive sensing device which has the ability to detect changes in the dielectric constant of the mixture when used in conjunction with appropriate ciruitry. It is necessary to pump ink through the sensor of this system, and therefore relatively large quantities of ink are required. Because of this pumping and flow requirement, the sensor must be physically large to allow an easy flow of ink and still maintain a high electrical capacitance. It would be desirable to have a smaller, less complex and highly portable system which lends itself both to laboratory use and to rapid, multiple-position measurements at an ink manufacturing or printing plant.